Reverse gear

ABSTRACT

A reverse gear for watercrafts includes an input shaft that receives rotational power of a main engine. A forward/reverse switching mechanism includes a reduction function and switches the rotational power of the input shaft among forward, neutral, and reverse states. An output shaft outputs the rotational power of the forward/reverse switching mechanism and rotates at a rotational speed that differs from a rotational speed of the input shaft due to the reduction function of the forward/reverse switching mechanism. A reduction mechanism includes a fixed reduction ratio, and reduces the rotational power of the output shaft and transmits the reduced rotational power to a propeller shaft. A forward/reverse housing accommodates the forward/reverse switching mechanism. A reduction housing accommodates the reduction mechanism. The forward/reverse housing and the reduction housing are detachably coupled one behind the other in an axial direction of the output shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2016-187427, filed Sep. 26, 2016. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to reverse gears for watercrafts that transmit rotational power of a main engine to a propeller. The present invention also relates to watercrafts equipped with such a reverse gear.

Discussion of the Background

Japanese Unexamined Patent Application Publication No. 7-17486 and Japanese Unexamined Utility Model Application Publication No. 6-78637 disclose reverse gears (marine gears) for watercrafts such as ski boats and pleasure boats. Such a reverse gear includes a forward clutch and a reverse clutch, which shift rotational power of an engine among forward rotation, neutral, and reverse rotation, and a reduction mechanism, which reduces the rotational power transmitted via the forward clutch or the reverse clutch and transmits the reduced rotational power to a propeller shaft.

The contents of Japanese Unexamined Patent Application Publication No. 7-17486 and Japanese Unexamined Utility Model Application Publication No. 6-78637 are incorporated herein by reference in their entirety.

It has been desired to achieve commonality of platforms (basic design) among models of the reverse gear as much as possible to reduce costs and effectively use resources by simplifying the process for producing the reverse gears. However, since the size of the reverse gear generally differs depending on models and specifications in accordance with the engine and the work capacity, the commonality of components and the ease in developing variations have not been considered. Unfortunately, such a situation does not respond to the increasing demand for cost reduction and effective use of resources.

Accordingly, it is a technical object of the present invention to provide a reverse gear that has been improved upon consideration of the above-mentioned current state and to provide a watercraft equipped with the reverse gear.

SUMMARY OF THE INVENTION

According to one aspect of the present invention for watercrafts, a reverse gear includes an input shaft, a forward/reverse switching mechanism, an output shaft, a reduction mechanism, a forward/reverse housing, and a reduction housing. The input shaft is configured to receive rotational power of a main engine. The forward/reverse switching mechanism includes a reduction function and is configured to switch the rotational power of the input shaft among forward, neutral, and reverse states. The output shaft is configured to output the rotational power of the forward/reverse switching mechanism and to rotate at a rotational speed that differs from a rotational speed of the input shaft due to the reduction function of the forward/reverse switching mechanism. The reduction mechanism includes a fixed reduction ratio and is configured to reduce the rotational power of the output shaft and to transmit the reduced rotational power to a propeller shaft. The forward/reverse housing accommodates the forward/reverse switching mechanism. The reduction housing accommodates the reduction mechanism. The forward/reverse housing and the reduction housing are detachably coupled one behind the other in an axial direction of the output shaft.

In the first aspect of the present invention, the forward/reverse switching mechanism may include at least one of an input gear group and an output gear group. The input gear group and the output gear group may each include a plurality of gears engaged with one another. The forward/reverse switching mechanism may include a reduction ratio that is changed by replacing at least one of the input gear group and the output gear group.

In the first aspect of the present invention, the forward/reverse switching mechanism may include a forward clutch and a reverse clutch that differ in a clutch size from each other.

According to the embodiment of the present invention, a reverse gear includes an input shaft, a forward/reverse switching mechanism, an output shaft, a reduction mechanism, a forward/reverse housing, and a reduction housing. The input shaft is configured to receive rotational power of a main engine. The forward/reverse switching mechanism includes a reduction function and is configured to switch the rotational power of the input shaft among forward, neutral, and reverse states. The output shaft is configured to output the rotational power of the forward/reverse switching mechanism and to rotate at a rotational speed that differs from a rotational speed of the input shaft due to the reduction function of the forward/reverse switching mechanism. The reduction mechanism includes a fixed reduction ratio and is configured to reduce the rotational power of the output shaft and to transmit the reduced rotational power to a propeller shaft. The forward/reverse housing accommodates the forward/reverse switching mechanism. The reduction housing accommodates the reduction mechanism. The forward/reverse housing and the reduction housing are detachably coupled one behind the other in an axial direction of the output shaft. Thus, in achieving commonality of platforms of the reverse gears among, for example, models, the reduction mechanism may have a common structure, and the forward/reverse switching mechanism may be changed with one that has a desired reduction ratio. That is, the reduction housing may be shared among different models and specifications, and the reverse gear may be easily applied to a plurality of models and specifications of the watercrafts only by developing variations of the forward/reverse housing. This eliminates the need for producing the reduction mechanism that differs depending on models and specifications and thus reduces the production costs of models and specifications as a whole. Additionally, since the reduction ratio of the reduction mechanism is fixed, the number of gears constituting the reduction mechanism is reduced to reduce the size of the reduction mechanism and the space occupied by the reduction mechanism. This consequently reduces the size of the entire reverse gear and the space occupied by the entire reverse gear. This configuration improves the versatility of the reverse gear and enables the reverse gear to be mounted on the watercraft that has a limited height.

With the reverse gear according to the embodiment of the present invention, the forward/reverse switching mechanism may include at least one of an input gear group and an output gear group. The input gear group and the output gear group may each include a plurality of gears engaged with one another. The reduction ratio of the forward/reverse switching mechanism may be changed by replacing at least one of the input gear group and the output gear group. In this case, although the reduction ratio of the reduction mechanism is fixed, a plurality of reduction ratios can be selected by the combination of the forward/reverse switching mechanism and the reduction mechanism in the entire reverse gear. Thus, while achieving the commonality of the reduction mechanism among models and specifications, the ease in variation development of the reverse gear is improved. This contributes to improving the versatility and increasing the range of application of the reverse gear.

With the reverse gear according to the embodiment of the present invention, the forward/reverse switching mechanism may include a forward clutch and a reverse clutch that differ in a clutch size from each other. In this case, by reducing the clutch size of the reverse clutch compared with the clutch size of the forward clutch, the size of the forward/reverse switching mechanism and the space occupied by the forward/reverse switching mechanism are reduced. This consequently further reduces the size of the reverse gear and the space occupied by the reverse gear.

With the watercraft according to the embodiment of the present invention, the reverse gear according to the embodiment of the present invention that reduces the production costs of models and specifications as a whole is mounted on a hull. This reduces the costs of the reverse gear and consequently reduces the production costs of the entire watercraft.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic side view of a ski boat;

FIG. 2 is a side view of a reverse gear according to a first embodiment;

FIG. 3 is a plan view of the reverse gear according to the first embodiment;

FIG. 4 is a schematic front view of the reverse gear according to the first embodiment illustrating how the gears are engaged;

FIG. 5 is a single-line diagram of a power transmission system of the reverse gear according to the first embodiment;

FIG. 6 is a side view of a reverse gear according to a second embodiment;

FIG. 7 is a plan view of the reverse gear according to the second embodiment;

FIG. 8 is a schematic front view of the reverse gear according to the second embodiment illustrating how the gears are engaged;

FIG. 9 is a side view of a reverse gear according to a third embodiment;

FIG. 10 is a plan view of the reverse gear according to the third embodiment;

FIG. 11 is a single-line diagram of a power transmission system of the reverse gear according to the third embodiment;

FIG. 12 is a side view of a reverse gear according to a fourth embodiment;

FIG. 13 is a plan view of the reverse gear according to the fourth embodiment;

FIG. 14 is a single-line diagram of a power transmission system of the reverse gear according to the fourth embodiment;

FIG. 15 is a single-line diagram of a power transmission system of a reverse gear according to a fifth embodiment;

FIG. 16 is a single-line diagram of a power transmission system of a reverse gear according to a sixth embodiment;

FIG. 17 is a side view of a reverse gear according to a seventh embodiment;

FIG. 18 is a plan view of the reverse gear according to the seventh embodiment;

FIG. 19 is a single-line diagram of a power transmission system of the reverse gear according to the seventh embodiment;

FIG. 20 is a side view of a reverse gear according to an eighth embodiment;

FIG. 21 is a single-line diagram of a power transmission system of the reverse gear according to the eighth embodiment;

FIG. 22 is a side view of a reverse gear according to a reference example;

FIG. 23 is a plan view of the reverse gear according to the reference example;

FIG. 24 is a schematic front view of the reverse gear of the reference example illustrating how the gears are engaged; and

FIG. 25 is a single-line diagram of a power transmission system of the reverse gear according to the reference example.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the drawings (FIGS. 1 to 8). In the following description, when terms indicating a specific direction or a position (for example, “left and right” and “up and down”) are used as required, the bow of a watercraft will be referred to as the front, the stern of the watercraft will be referred to as the rear, and the front and rear are used as a reference. The watercraft is a ski boat 1 in this embodiment. The terms are used for convenience of the description and do not intend to limit the technical range of the present invention.

First, the overview of the watercraft, which is the ski boat 1 in this embodiment, will be described with reference to FIG. 1. As illustrated in FIG. 1, the ski boat 1 includes a hull 2, a cockpit 3, a rudder 4, and a propeller 5. The cockpit 3 is located on the upper surface of the hull at the center. The rudder 4 is provided on the bottom of the hull 2 at the watercraft's stern. The propeller 5 is located in front of the rudder 4 on the bottom of the hull 2 at the watercraft's stern. A propeller shaft 6 is supported on the bottom of the hull 2 at the watercraft's stern. The propeller shaft 6 rotates the propeller 5. The propeller 5 is secured to the projecting end of the propeller shaft 6.

Although detailed illustration is omitted, a steering wheel, a forward/reverse manipulator, a dead-slow travel manipulator, and a speed manipulator are provided in the cockpit 3. The steering wheel changes the traveling direction of the hull 2 to left and right by steering. The forward/reverse manipulator shifts the traveling direction of the hull 2 between forward and reverse. The forward/reverse manipulator is a forward/reverse lever. The dead-slow travel manipulator causes the hull 2 to travel at dead slow. The dead-slow travel manipulator is a trawling lever. The speed manipulator sets and maintains the output rotational speed of an internal-combustion engine 10, which will be discussed below. The speed manipulator is a throttle lever. The manipulators are not limited to the levers, but may be in other forms such as dials. An occupant's space S is provided at the rear section of the cockpit 3. For example, a seat 7 is located in the occupant's space S.

A main engine, that is, a drive source of the propeller 5 is the engine 10. The engine 10 and a reverse gear 11 are provided on the inner bottom portion of the hull 2 at the watercraft's stern. The reverse gear 11 transmits the rotational power of the engine 10 to the propeller 5. The rotational power transmitted to the propeller shaft 6 from the engine 10 via the reverse gear 11 drivingly rotates the propeller 5. The reverse gear 11 of the embodiment is a V-drive system in which, as viewed from the side, the shaft angle of the propeller shaft 6 is set to an acute angle (the angle between an input shaft 13 (or an output shaft 16) and the propeller shaft 6 is set to an acute angle as viewed from the side). The reverse gear 11 is located in front of the engine 10.

FIGS. 2 to 5 illustrate the reverse gear 11 according to a first embodiment. As illustrated in FIGS. 2 to 5, the reverse gear 11 of the first embodiment includes the input shaft 13, a forward/reverse switching mechanism 20, the output shaft 16, and a reduction mechanism 17. The input shaft 13 is coupled to a flywheel 12 of the engine 10. The forward/reverse switching mechanism 20 switches the rotational power of the input shaft 13 among forward, neutral, and reverse states. The output shaft 16 outputs the rotational power of the forward/reverse switching mechanism 20. The reduction mechanism 17 reduces the rotational power of the output shaft 16 and transmits the reduced rotational power to the propeller shaft 6.

An outer case of the reverse gear 11 includes a clutch lid member 18 a, a hollow box-like forward/reverse housing 18 b, a hollow reduction housing 18 c, and a reduction lid member 18 d. The clutch lid member 18 a is located at the rear section. The hollow reduction housing 18 c is L-shaped as viewed from the side. The reduction lid member 18 d is located at the front section. The clutch lid member 18 a is detachably coupled to the rear surface of the forward/reverse housing 18 b with a plurality of bolts. The front surface of the forward/reverse housing 18 b is detachably coupled to the rear surface of the body portion of the reduction housing 18 c with a plurality of bolts. The front surface of the reduction housing 18 c is detachably coupled to the reduction lid member 18 d with a plurality of bolts. The forward/reverse housing 18 b accommodates, for example, the input shaft 13, the upstream section of the output shaft 16, and the forward/reverse switching mechanism 20. The reduction housing 18 c accommodates the downstream section of the output shaft 16, the reduction mechanism 17, and the upstream section of the propeller shaft 6. The input shaft 13 projects rearward from the rear surface of the clutch lid member 18 a. The propeller shaft 6 projects diagonally downward and rearward from the rear surface of a downwardly extending portion of the reduction housing 18 c and projects from the watercraft's bottom. The lower the height of the upper surfaces of the lid members 18 a and 18 d and the housings 18 b and 18 c, the more spacious the inside of the watercraft such as the occupant's space S in the watercraft (refer to FIG. 1).

An input gear 13 a is fixed to the front end section of the input shaft 13. The input gear 13 a is constantly engaged with an input relay gear 14 g. The input relay gear 14 g is fixed to the rear end section of a forward clutch shaft 14 f. The forward clutch shaft 14 f extends parallel to the input shaft 13. A forward clutch 14 is located on the forward clutch shaft 14 f and includes steel plates 14 d and friction plates 14 e that are alternately arranged. The forward clutch 14 includes a forward case 14 a to which the steel plates 14 d are attached, a forward tube 14 b to which the friction plates 14 e are attached, and a forward clutch cylinder 14 c. The friction plates 14 e are capable of being brought into contact with the steel plates 14 d under pressure. The forward clutch cylinder 14 c generates contact pressure using hydraulic oil pressure. The forward case 14 a is fixed to the forward clutch shaft 14 f. The forward tube 14 b is loosely fitted to the forward clutch shaft 14 f to be rotational. The rear end section of the forward tube 14 b is inserted in the inner circumference of the forward case 14 a. A forward gear 42 is integrally formed with the outer circumference of the forward case 14 a. A forward reduction gear 43 is integrally formed at the front end section of the forward tube 14 b. The forward clutch shaft 14 f configures a support shaft of the forward clutch 14. A hydraulic pump 19 is coupled to the front end section of the forward clutch shaft 14 f. The hydraulic pump 19 supplies hydraulic oil to the forward clutch 14 and a reverse clutch 15.

The reverse clutch 15 is located on a reverse clutch shaft 15 f. The reverse clutch shaft 15 f extends parallel to the input shaft 13. Like the forward clutch 14, the reverse clutch 15 includes steel plates 15 d and friction plates 15 e that are alternately arranged. The reverse clutch 15 includes a reverse case 15 a to which the steel plates 15 d are attached, a reverse tube 15 b to which the friction plates 15 e are attached, and a reverse clutch cylinder 15 c. The friction plates 15 e are capable of being brought into contact with the steel plates 15 d under pressure. The reverse clutch cylinder 15 c generates contact pressure using hydraulic oil pressure. The reverse case 15 a is fixed to the reverse clutch shaft 15 f. The reverse tube 15 b is loosely fitted to the reverse clutch shaft 15 f to be rotational. The rear end section of the reverse tube 15 b is inserted in the inner circumference of the reverse case 15 a. A reverse gear 44 is integrally formed with the outer circumference of the reverse case 15 a. A reverse reduction gear 45 is integrally formed with the front end section of the reverse tube 15 b. The reverse gear 44 is constantly engaged with the forward gear 42 of the forward clutch 14. The forward reduction gear 43 and the reverse reduction gear 45 are constantly engaged with an output gear 46. The output gear 46 is fixed to the rear end section of the output shaft 16. The reverse clutch shaft 15 f configures the support shaft of the reverse clutch 15.

The forward/reverse switching mechanism 20 has a reduction function that, in the forward state, reduces the rotational power of the input shaft 13 in accordance with the reduction ratio of the input gear 13 a and the input relay gear 14 g and the reduction ratio of the forward reduction gear 43 and the output gear 46 and transmits the reduced rotational power to the output shaft 16. Additionally, the forward/reverse switching mechanism 20 has a reduction function that, in the reverse state, reduces the rotational power of the input shaft 13 in accordance with the reduction ratio of the input gear 13 a and the input relay gear 14 g, the reduction ratio of the forward gear 42 and the reverse gear 44, and the reduction ratio of the reverse reduction gear 45 and the output gear 46 and transmits the reduced rotational power to the output shaft 16.

The forward clutch 14 and the reverse clutch 15 are hydraulic friction clutches and, more specifically, are multiplate wet clutches. The forward clutch 14 and the reverse clutch 15 have different clutch sizes from each other. Generally, since the reverse traveling does not require a great propulsive force compared with the forward traveling, the clutch size of the reverse clutch 15 is smaller than the clutch size of the forward clutch 14 in this embodiment.

The input gear 13 a and the input relay gear 14 g configure an input gear group. The forward reduction gear 43, the reverse reduction gear 45, and the output gear 46 configure an output gear group. In this embodiment, the gears 13 a, 14 g, 42, 43, 44, 45, and 46 are all helical gears in which teeth are cut at an angle with respect to the axis. The gears may be other gears such as spur gears.

The front end section of the output shaft 16 and the front end section of the propeller shaft 6 are rotationally supported in the reduction housing 18 c. A reduction drive gear 31 is fixed to the front end section of the output shaft 16. A reduction output gear 35 is fixed to the front end section (upstream section) of the propeller shaft 6. The reduction drive gear 31 of the output shaft 16 is constantly engaged with the reduction output gear 35 of the propeller shaft 6. The reduction mechanism 17 has a reduction function that reduces the rotational power of the output shaft 16 in accordance with the reduction ratio of the reduction drive gear 31 and the reduction output gear 35 and transmits the reduced rotational power to the propeller shaft 6.

The reduction drive gear 31 and the reduction output gear 35 are conical gears in which teeth are axially and continuously profile-shifted into a conical shape. The reduction drive gear 31 and the reduction output gear 35 configure the reduction mechanism 17 having a fixed reduction ratio. The rotational power of the output shaft 16 is reduced to the fixed reduction ratio and transmitted to the propeller shaft 6 by the engagement between the reduction drive gear 31 and the reduction output gear 35. Employing a plurality of conical gears as the gears constituting the reduction mechanism 17 allows the shaft angle of the propeller shaft 6 to be set to various angles as viewed from the side depending on the combination of the plurality of conical gears. For example, in the ski boat 1, the shaft angle of the propeller shaft 6 can be easily increased.

Next, operation of the reverse gear 11 will be described. When the forward/reverse lever in the cockpit 3 (refer to FIG. 1) is manipulated to a forward, reverse, or neutral position, the supply destination of the hydraulic oil is shifted to the forward clutch 14 (the forward clutch cylinder 14 c), the reverse clutch 15 (the reverse clutch cylinder 15 c), or neutral.

When the forward/reverse lever is manipulated to the forward position, the forward clutch 14 is brought into a power connected state (the steel plates 14 d of the forward case 14 a and the friction plates 14 e of the forward tube 14 b are pressed together using the hydraulic oil pressure), and the reverse clutch 15 is in a power disconnected state. Thus, the forward clutch 14 allows the forward reduction gear 43 to integrally rotate with the forward clutch shaft 14 f. In this case, the rotational power of the engine 10 is transmitted from the input shaft 13 to the output shaft 16 via the forward clutch shaft 14 f and the forward clutch 14 and is transmitted from the output shaft 16 to the propeller shaft 6 via the reduction mechanism 17. As a result, the watercraft 1 is brought into a forward state in which the rotational power of the engine 10 is transmitted to the propeller shaft 6 as the output in the forward direction. The forward traveling speed of the watercraft 1 during normal traveling is adjusted by the throttle lever in the cockpit 3.

In the forward state, the rotational power of the input shaft 13 is reduced in accordance with the reduction ratio of the input gear 13 a and the input relay gear 14 g and the reduction ratio of the forward reduction gear 43 and the output gear 46 and is transmitted to the output shaft 16. The rotational power of the output shaft 16 is reduced in accordance with the reduction ratio of the reduction mechanism 17 (the reduction drive gear 31 and the reduction output gear 35) and is transmitted to the propeller shaft 6.

When the forward/reverse lever is manipulated to the reverse position, the reverse clutch 15 is brought into the power connected state (the steel plates 15 d of the reverse case 15 a and the friction plates 15 e of the reverse tube 15 b are pressed together using the hydraulic oil pressure), and the forward clutch 14 is in the power disconnected state. Thus, the reverse clutch 15 allows the reverse reduction gear 45 to integrally rotate with the reverse clutch shaft 15 f. In this case, the rotational power of the engine 10 is transmitted from the input shaft 13 to the output shaft 16 via the forward clutch shaft 14 f, the reverse clutch shaft 15 f, and the reverse clutch 15. The output shaft 16 rotates in reverse to the input shaft 13, and the reverse rotational power of the output shaft 16 is transmitted to the propeller shaft 6 via the reduction mechanism 17. As a result, the watercraft 1 is brought into a reverse state in which the rotational power of the engine 10 is transmitted to the propeller shaft 6 as the output in the reverse direction. The reverse traveling speed of the watercraft 1 during normal traveling is also adjusted by the throttle lever.

In the reverse state, the rotational power of the input shaft 13 is reduced in accordance with the reduction ratio of the input gear 13 a and the input relay gear 14 g, the reduction ratio of the forward gear 42 and the reverse gear 44, and the reduction ratio of the reverse reduction gear 45 and the output gear 46 and is transmitted to the output shaft 16. The rotational power of the output shaft 16 is reduced in accordance with the reduction ratio of the reduction mechanism 17 and is transmitted to the propeller shaft 6.

When the forward/reverse lever is manipulated to the neutral position so that the forward clutch 14 and the reverse clutch 15 are brought into the power disconnected state, the watercraft 1 is brought into a neutral state in which the rotational power of the engine 10 is not transmitted to the output shaft 16 and thus not transmitted to the propeller shaft 6. Although both the clutches 14 and 15 are in the power disconnected state, the rotational power of the input shaft 13 is transmitted to the forward clutch shaft 14 f via the input gear 13 a and the input relay gear 14 g. Thus, the hydraulic pump 19, which is coupled to the front end section of the forward clutch shaft 14 f, is operated.

As clearly shown in the above description and FIGS. 2 to 5, the reverse gear 11 includes the input shaft 13, the forward/reverse switching mechanism 20, the output shaft 16, and the reduction mechanism 17. The input shaft 13 receives the rotational power of the main engine, which is the engine 10 in this embodiment. The forward/reverse switching mechanism 20 switches the rotational power of the input shaft 13 among the forward, neutral, and reverse states. The output shaft 16 outputs the rotational power of the forward/reverse switching mechanism 20. The reduction mechanism 17 reduces the rotational power of the output shaft 16 and transmits the reduced rotational power to the propeller shaft 6. In the reverse gear 11, the forward/reverse housing 18 b, which accommodates the forward/reverse switching mechanism 20, and the reduction housing 18 c, which accommodates the reduction mechanism 17, are detachably coupled one behind the other in the axial direction of the output shaft 16. The forward/reverse switching mechanism 20 has the reduction function so that the rotational speed of the input shaft 13 differs from the rotational speed of the output shaft 16, and the reduction ratio of the reduction mechanism 17 is fixed. Thus, in achieving commonality of the platform of the reverse gear 11 among, for example, models, the reduction mechanism 17 may have a common structure, and the forward/reverse switching mechanism 20 may be changed to one that has a desired reduction ratio. That is, the reduction housing 18 c may be shared among different models and specifications, and the reverse gear 11 may be easily applied to a plurality of models and specifications of the watercrafts such as the ski boat 1 only by developing variations of the forward/reverse housing 18 b. This eliminates the need for producing the reduction mechanism 17 that differs depending on models and specifications and thus reduces the production costs of models and specifications as a whole.

In the reverse gear 11, the rotational power of the output shaft 16 is transmitted to the propeller shaft 6 by the engagement between the reduction drive gear 31, which is provided on the output shaft 16, and the reduction output gear 35, which is provided on the propeller shaft 6, and the reduction mechanism 17 has the fixed reduction ratio. Thus, although a desired reduction ratio of the entire reverse gear 11 is obtained depending on the combination of the forward/reverse switching mechanism 20, which has the reduction function, and the reduction mechanism 17, the number of the gears constituting the reduction mechanism 17 is reduced to reduce the size of the reduction mechanism 17 and the space occupied by the reduction mechanism 17 and to consequently reduce the size of the entire reverse gear 11 and the space occupied by the entire reverse gear 11. This configuration improves the versatility of the reverse gear 11 and enables the reverse gear 11 to be mounted on the watercraft 1 that has a limited height.

The size of the reduction mechanism 17 and the space occupied by the reduction mechanism 17 are reduced by reducing the number of the gears constituting the reduction mechanism 17. For example, the height of the reduction housing 18 c and the reduction lid member 18 d is reduced, and the length of the reduction housing 18 c is reduced in the axial direction. This configuration increases the space in the watercraft such as the occupant's space S so that, for example, a space for mounting the seat 7 (refer to FIG. 1) is provided above the reduction mechanism 17 and enables the reverse gear 11 to be mounted on the watercraft 1 that has a limited height.

In the reverse gear 11, the forward/reverse switching mechanism 20 includes the input gear group (the input gear 13 a and the input relay gear 14 g) and the output gear group (the forward reduction gear 43, the reverse reduction gear 45, and the output gear 46). The input gear group and the output gear group are configured by a plurality of gears engaged with one another. The reduction ratio of the forward/reverse switching mechanism 20 is changed by replacing at least one of the input gear group and the output gear group. The replacement of at least one of the input gear group and the output gear group consequently changes the reduction ratio of the entire reverse gear 11. Thus, a plurality of reduction ratios can be selected by the combination of the forward/reverse switching mechanism 20 and the reduction mechanism 17 without changing the reduction ratio of the reduction mechanism 17. This configuration improves the ease in variation development of the reverse gear 11 while achieving the commonality of the reduction mechanism 17, the lid members 18 a and 18 d, and the housings 18 b and 18 c among models and specifications and contributes to improving the versatility and increasing the range of application of the reverse gear 11.

In the reverse gear 11, as long as the forward/reverse switching mechanism 20 includes the forward clutch 14 and the reverse clutch 15 that have different clutch sizes from each other, the clutch size of the reverse clutch 15 may be smaller than the clutch size of the forward clutch 14. Thus, the size of the forward/reverse switching mechanism 20 is reduced, and the space occupied by the forward/reverse switching mechanism 20 is reduced. This consequently further reduces the size of the reverse gear 11 and the space occupied by the reverse gear 11.

FIGS. 6 to 8 illustrate a reverse gear 11 according to a second embodiment. In the second embodiment, the forward clutch 14 and the reverse clutch 15 are arranged next one another in the lateral direction. The second embodiment differs from the first embodiment in that the input shaft 13 and the output shaft 16 are coaxially arranged. The single-line diagram of the power transmission system of the second embodiment is the same as FIG. 5.

In the reverse gear 11 of the second embodiment, since the input shaft 13 and the output shaft 16 are coaxially arranged, and the forward clutch 14 and the reverse clutch 15 are arranged next to one another in the lateral direction, the height of the forward/reverse switching mechanism 20 and the reduction mechanism 17 is reduced, and the shape of the left and right sides of the forward/reverse housing 18 b is well-balanced. This configuration further reduces the size of the reverse gear 11, improves the versatility of the reverse gear 11, and enables the reverse gear 11 to be mounted on the watercraft 1 that has a limited height.

The sizes of the clutches 14 and 15 are the same in the reverse gear 11 of the second embodiment. However, the forward/reverse switching mechanism 20 may include the forward clutch 14 and the reverse clutch 15 that have different clutch sizes from each other in the above-described second embodiment. For example, the clutch size of the reverse clutch 15 may be smaller than the clutch size of the forward clutch 14. In the reverse gear 11 of the second embodiment, the gears 13 a, 14 g, 42, 43, 44, 45, and 46 are spur gears in which teeth are cut to be parallel to the axis. However, the gears may be other gears such as helical gears.

FIGS. 9 to 11 illustrate a reverse gear 11 according to a third embodiment. In the third embodiment, compared with the above-described first embodiment, the output shaft 16 is separable in the axial direction into front and rear sections. In this case, the output shaft 16 is divided into an upstream section and a downstream section. The front end portion of the upstream output shaft 16 and the rear end portion of the downstream output shaft 16 are coupled to each other with a coupling 27 to be slidable in the axial direction and not to rotate relative to each other (spline-fitted). Thus, when the plurality of bolts that couple the forward/reverse housing 18 b to the reduction housing 18 c are removed to separate the forward/reverse housing 18 b from the reduction housing 18 c, the output shaft 16 is separated into the section corresponding to the forward/reverse housing 18 b and the section corresponding to the reduction housing 18 c. That is, the forward/reverse housing 18 b and the reduction housing 18 c are easily separated without changing the structure in the forward/reverse housing 18 b and the structure in the reduction housing 18 c.

Like the above-described third embodiment, the output shaft 16 may be separable in the axial direction and coupled with the coupling 27 to prevent relative rotation in the above-described second embodiment.

FIGS. 12 and 13 illustrate a reverse gear 11 according to a fourth embodiment. In the fourth embodiment, compared with the above-described second embodiment, the output shaft 16 is separable in the axial direction into front and rear sections. The front and rear sections of the output shaft 16 are coupled to each other with the coupling 27 to be slidable in the axial direction and not rotate relative to each other. The reduction mechanism 17 inside the reduction housing 18 c includes an idling shaft 32. The idling shaft 32 is rotationally supported between the front end section of the output shaft 16 and the front end section of the propeller shaft 6. The output shaft 16, the idling shaft 32, and the propeller shaft 6 are aligned with each other in plan view. A first idling gear 33 and a second idling gear 34 are fixed to the idling shaft 32. The reduction drive gear 31 is fixed to the front end section of the output shaft 16 (the front end section of the downstream output shaft 16). The reduction output gear 35 is fixed to the front end section (upstream section) of the propeller shaft 6. The reduction drive gear 31 of the output shaft 16 is constantly engaged with the first idling gear 33 of the idling shaft 32. The second idling gear 34 of the idling shaft 32 is constantly engaged with the reduction output gear 35 of the propeller shaft 6.

The reduction drive gear 31, the pair of idling gears 33 and 34, and the reduction output gear 35 are conical gears. The gears 31, 33, 34, and 35 configure the reduction mechanism 17 having a fixed reduction ratio. The rotational power of the output shaft 16 is reduced to the fixed reduction ratio by the reduction drive gear 31, the pair of idling gears 33 and 34, and the reduction output gear 35. Employing the plurality of conical gears as gears constituting the reduction mechanism 17 facilitates setting the shaft angle of the propeller shaft 6 to various angles as viewed from the side depending on the combination of the plurality of conical gears. For example, the shaft angle of the propeller shaft 6 is easily increased in the ski boat 1. The reduction mechanism 17 may include a plurality of conical gears having the same angle coupled to each other, or may include a plurality of conical gears having different angles coupled to each other.

In the above-described fourth embodiment also, the forward/reverse housing 18 b, which accommodates the forward/reverse switching mechanism 20, and the reduction housing 18 c, which accommodates the reduction mechanism 17, are detachably coupled one behind the other in the axial direction of the output shaft 16. Since the forward/reverse switching mechanism 20 has a reduction function, the rotational speed of the input shaft 13 differs from the rotational speed of the output shaft 16. Thus, in achieving commonality in the platform of the reverse gear 11 among, for example, models, the reduction mechanism 17 may have a common structure, and the forward/reverse switching mechanism 20 may be changed to one that has a desired reduction ratio. This eliminates the need for producing the reduction mechanism 17 that differs depending on models and specifications and reduces the production costs of models and specifications as a whole. Since the reduction ratio of the reduction mechanism 17 is fixed, the number of the gears constituting the reduction mechanism 17 is reduced in order to reduce the size of the reduction mechanism 17 and the space occupied by the reduction mechanism 17. This consequently reduces the size of the entire reverse gear 11 and the space occupied by the entire reverse gear 11.

Like the above-described fourth embodiment, in the above-described first embodiment and the above-described third embodiment, the idling shaft 32 may be rotationally supported between the front end section of the output shaft 16 and the front end section of the propeller shaft 6 to reduce the rotational power of the output shaft 16 to the fixed reduction ratio by the reduction drive gear 31, the pair of idling gears 33 and 34, and the reduction output gear 35.

FIGS. 15 and 16 illustrate a reverse gear 11 according to fifth and sixth embodiments based on the above-described third embodiment. In the fifth embodiment illustrated in FIG. 15, the forward reduction gear 43, the reverse reduction gear 45, and the output gear 46 are conical gears, and the output shaft 16 is tilted. In the sixth embodiment illustrated in FIG. 16, the forward reduction gear 43, the reverse reduction gear 45, and the output gear 46 are conical gears, and the reduction drive gear 31 and the reduction output gear 35 are spur gears. The output shaft 16 is tilted to extend parallel to the propeller shaft 6. In these embodiments, although the output shaft 16 is not parallel to, for example, the input shaft 13 and is not positioned on the same plane as, for example, the input shaft 13, there is no significant influence on reducing the height of the housings 18 b and 18 c as long as the inclination of the output shaft 16 is within the range that allows the output shaft 16 to be fitted in the reduction housing 18 c. In the above-described fifth and sixth embodiments, the output shaft 16 may be a single shaft not separated in the axial direction into a front section and a rear section.

Next, a reverse gear 11 according to a seventh embodiment will be described with reference to FIGS. 17 to 19. The reverse gear 11 of the seventh embodiment differs from the reverse gear 11 of the above-described fourth embodiment in the configuration of the forward/reverse switching mechanism 20. As illustrated in FIGS. 17 to 19, the reverse gear 11 of the seventh embodiment includes the forward clutch 14 and a reverse brake 61 as the forward/reverse switching mechanism 20, which shifts the rotational power of the input shaft 13 among the forward, neutral, and reverse states. The forward/reverse switching mechanism 20 is accommodated in the forward/reverse housing 18 b. In the reverse state in which the output shaft 16 is rotated in reverse to the input shaft 13, the forward/reverse switching mechanism 20 has a reduction function in which the rotational power of the input shaft 13 is reduced and transmitted to the output shaft 16.

In the reverse gear 11 of the seventh embodiment, the input shaft 13 and the output shaft 16 are coaxially arranged. The forward clutch 14 is located on the outer circumference of the output shaft 16, and the reverse brake 61 is located on the outer circumference of the forward clutch 14. The forward clutch 14 is a hydraulic friction clutch and, more specifically, is a multiplate wet clutch. The reverse brake 61 is a hydraulic friction brake and, more specifically, is a multiplate wet brake.

The forward clutch 14 is located at an upstream section of the output shaft 16, which extends coaxially with the input shaft 13, and includes the steel plates 14 d and the friction plates 14 e, which are alternately arranged. The forward clutch 14 includes the forward case 14 a to which the steel plates 14 d are attached, the forward tube 14 b, which is fixed to the forward case 14 a, and the forward clutch cylinder 14 c, which generates contact pressure (clutch pressure) using the hydraulic oil pressure. The forward case 14 a is fixed to the input shaft 13. The rear end section of the output shaft 16 is inserted in the inner circumference of the forward case 14 a. The rear end section of the output shaft 16 is rotationally supported by the inner circumference of the forward case 14 a. The friction plates 14 e, which are capable of being brought into contact with the steel plates 14 d under pressure, are provided on the outer circumferential portion of the rear end section of the output shaft 16. The forward tube 14 b is rotationally fitted to the output shaft 16. A reverse drive gear 21 is integrally formed on the outer circumferential portion of the front end section of the forward tube 14 b.

The reverse brake 61 is located on the outer circumference of the forward clutch 14 to overlap the forward clutch 14 and includes, like the forward clutch 14, steel plates 61 d and friction plates 61 e that are alternately arranged. The reverse brake 61 includes a reverse case 61 a to which steel plates 61 d are attached and a reverse brake cylinder 61 c. The reverse brake cylinder 61 c generates contact pressure by the hydraulic oil pressure. The reverse case 61 a is secured in the forward/reverse housing 18 b. The forward case 14 a is positioned on the inner circumference of the reverse case 61 a. The friction plates 61 e, which are capable of being brought into contact with the steel plates 61 d under pressure, are provided on the outer circumferential portion of a rear-facing annular projection 23 a formed on a carrier 23, which will be discussed below. The carrier 23 is loosely fitted to the forward tube 14 b to be rotational.

A planetary reversing gear mechanism 22 is located on the output shaft 16 downstream of the forward clutch 14 and the reverse brake 61 (at a position close to the front of the rear section). The planetary reversing gear mechanism 22 includes the carrier 23, which rotationally supports a plurality of sets of planetary gears 24 and reversing gears 25. As is mentioned above, the carrier 23 is loosely fitted to the forward tube 14 b to be rotational. The group of planetary gears 24 are positioned on the front side of the carrier 23 at the same radial distance from the common axis. The group of reversing gears 25 are positioned on the front side of the carrier 23 at the same radial distance from the common axis. The radial distance between the axis and the planetary gears 24 is different from the radial distance between the axis and the planetary gears 25. The planetary gears 24 of the carrier 23 are constantly engaged with the reverse drive gear 21 of the forward tube 14 b from radially outward. The planetary gears 24 are also constantly engaged with the corresponding reversing gears 25. The reversing gears 25 are constantly engaged with a reverse driven gear 26. The reverse driven gear 26 is fixed to the output shaft 16 at a position close to the front of the rear section.

Like the above-described third to sixth embodiments, the output shaft 16 of the seventh embodiment is separable in the axial direction into a front section and a rear section. The front and rear sections are coupled to each other with the coupling 27 to be slidable in the axial direction and not to rotate relative to each other. The configuration of the reduction mechanism 17, which is accommodated in the reduction housing 18 c, is the same as the reduction mechanism 17 of the fourth embodiment described with reference to FIGS. 12 to 14.

When the forward/reverse lever in the cockpit 3 is manipulated to the forward, reverse, or neutral position, the supply destination of the hydraulic oil is shifted to the forward clutch 14 (the forward clutch cylinder 14 c), the reverse brake 61 (the reverse brake cylinder 61 c), or neutral.

When the forward/reverse lever is manipulated to the forward position, and the forward clutch 14 is brought into the power connected state (the steel plates 14 d of the forward case 14 a and the friction plates 14 e of the output shaft 16 are pressed together using the hydraulic oil pressure), the reverse brake 61 is in the power disconnected state. Thus, the forward clutch 14 allows the input shaft 13 to rotate integrally with the output shaft 16. In this case, the rotational power of the engine 10 is transmitted from the input shaft 13 to the output shaft 16 via the forward clutch 14. The rotational power transmitted to the output shaft 16 is transmitted to the propeller shaft 6 via the reduction mechanism 17. As a result, the watercraft 1 is brought into the forward state in which the rotational power of the engine 10 is transmitted to the propeller shaft 6 as the output in the forward direction. The forward traveling speed of the watercraft 1 during normal traveling is adjusted by the throttle lever in the cockpit 3. When the forward clutch 14 is in the power connected state, the rotation direction and the rotational speed of the reverse drive gear 21 and the reverse driven gear 26 are the same. Thus, the group of the planetary gears 24 and the group of the reversing gears 25 do not rotate, and the carrier 23 rotates in the same rotation direction and at the same rotational speed as the output shaft 16.

When the forward/reverse lever is manipulated to the reverse position, and the reverse brake 61 is brought into the power connected state, the forward clutch 14 is in the power disconnected state, and the carrier 23 is secured to the reverse case 61 a. Thus, the rotational power of the engine 10 is transmitted from the input shaft 13 to the planetary gears 24 of the carrier 23 via the reverse drive gear 21 of the forward tube 14 b. The rotational power transmitted to the planetary gears 24 is transmitted to the reverse driven gear 26 of the output shaft 16 via the reversing gears 25. Thus, the output shaft 16 is rotated in reverse to the input shaft 13, and the reverse rotational power of the output shaft 16 is transmitted to the propeller shaft 6 via the reduction mechanism 17. As a result, the watercraft 1 is brought into the reverse state in which the rotational power of the engine 10 is transmitted to the propeller shaft 6 as the output in the reverse direction. The reverse traveling speed of the watercraft 1 during normal traveling is also adjusted by the throttle lever. In the reverse state, the rotational power of the input shaft 13 is reduced by the forward/reverse switching mechanism 20 in accordance with the reduction ratio of the planetary reversing gear mechanism 22 and is transmitted to the output shaft 16.

When the forward/reverse lever is manipulated to the neutral position so that the forward clutch 14 and the reverse brake 61 are both brought into the power disconnected state, the watercraft 1 is brought into the neutral state in which the rotational power of the engine 10 is not transmitted to the output shaft 16 and thus not transmitted to the propeller shaft 6.

In the above-described seventh embodiment, as clearly shown in the above description and FIGS. 17 to 19, the forward/reverse housing 18 b, which accommodates the forward/reverse switching mechanism 20, and the reduction housing 18 c, which accommodates the reduction mechanism 17, are detachably coupled one behind the other in the axial direction of the output shaft 16. The forward/reverse switching mechanism 20 has a reduction function so that the rotational speed of the input shaft 13 differs from the rotational speed of the output shaft 16 in the reverse state, and the reduction mechanism 17 has a fixed reduction ratio. Thus, in achieving commonality of the platform of the reverse gear 11 among, for example, models, the reduction mechanism 17 may have a common structure, and the forward/reverse switching mechanism 20 may be changed to one that has a desired reduction ratio. That is, the reduction housing 18 c may be shared among different models and specifications, and the reverse gear 11 may be easily applied to a plurality of models and specifications of the watercrafts such as the ski boat 1 only by developing variations of the forward/reverse housing 18 b. This eliminates the need for producing the reduction mechanism 17 that differs depending on models and specifications and thus reduces the production costs of models and specifications as a whole.

Additionally, in the above-described seventh embodiment, the input shaft 13 and the output shaft 16 are coaxially arranged, the forward clutch 14 is located on the outer circumference of the output shaft 16, the reverse brake 61 is located on the outer circumference of the forward clutch 14, and the planetary reversing gear mechanism 22 is located on the output shaft 16 downstream of the forward clutch 14 and the reverse brake 61. Thus, in the reverse gear 11, the height of the housings 18 b and 18 c, which accommodate the input shaft 13, the forward clutch 14, the reverse brake 61, and the output shaft 16, is reduced, and the length of the housings 18 b and 18 c in the axial direction is reduced, resulting in reduction of the size of the reverse gear 11. This configuration improves the versatility of the reverse gear 11 and enables the reverse gear 11 to be mounted on the watercraft 1 that has a limited height.

Additionally, in the reverse gear 11 of the seventh embodiment, the forward/reverse switching mechanism 20 includes the output gear groups (the reverse drive gear 21, the planetary gears 24, the reversing gears 25, and the reverse driven gear 26) in which a plurality of gears are engaged with one another. By replacing the engaged one of the gear groups (at least one of the group of the reverse drive gear 21 and the planetary gears 24, the group of the planetary gears 24 and the reversing gears 25, and the group of the reversing gears 25 and the reverse driven gear 26), the reduction ratio of the forward/reverse switching mechanism 20 in the reverse state is changed, and the reduction ratio of the entire reverse gear 11 in the reverse state is consequently changed. Thus, a plurality of reduction ratios can be selected by the combination of the forward/reverse switching mechanism 20 and the reduction mechanism 17 without changing the reduction ratio of the reduction mechanism 17. Thus, while achieving the commonality of the reduction mechanism 17, the lid members 18 a and 18 d, and the housings 18 b and 18 c among models and specifications, the ease in variation development of the reverse gear 11 is improved. This contributes to improving the versatility and increasing the range of application of the reverse gear 11.

In the reverse gear 11 of the seventh embodiment, the gears of the forward/reverse switching mechanism 20 may be spur gears or helical gears.

FIGS. 20 and 21 illustrate a reverse gear 11 according to an eighth embodiment based on the seventh embodiment. As illustrated in FIGS. 20 and 21, if the conical angle of the reduction drive gear 31 and the reduction output gear 35 of the reduction mechanism 17 is greater than a certain value, the idling shaft 32 and the pair of idling gears 33 and 34 may be omitted, and the reduction drive gear 31 and the reduction output gear 35 may be directly engaged with each other like the above-described first to third embodiments. In this manner, reducing the number of the gears constituting the reduction mechanism 17 reduces the height of the reduction housing 18 c and the reduction lid member 18 d and reduces the length of the reduction housing 18 c in the axial direction. Thus, the internal space such as the occupant's space S (refer to FIG. 1) is increased. This configuration provides the space for placing the seat 7 above the reduction mechanism 17 and enables the reverse gear 11 to be mounted on the watercraft 1 that has a limited height.

Next, a reverse gear 50 according to a reference example will be described with reference to FIGS. 22 to 25. In the reverse gear 50 of the reference example, the input gear 13 a, which is fixed to the front end section of the input shaft 13, is constantly engaged with the input relay gear 14 g, which is fixed to the rear end section of a reverse output shaft 51. The reverse output shaft 51 extends parallel to the input shaft 13. The input relay gear 14 g, the forward reduction gear 43, and the reverse reduction gear 45 are provided on the reverse output shaft 51 in this order from the upstream end. The input relay gear 14 g is fixed to the reverse output shaft 51. The forward reduction gear 43 is loosely fitted to the reverse output shaft 51 and is coupled by the forward clutch 14, which is a multiplate wet clutch, to be capable of connecting and disconnecting power. The reverse reduction gear 45 is loosely fitted to the reverse output shaft 51 and is coupled by the reverse clutch 15, which is a multiplate wet clutch, to be capable of connecting and disconnecting power. The forward reduction gear 43 is constantly engaged with a forward relay gear 53 fixed to the rear end section of a forward output shaft 52. The forward output shaft 52 extends parallel to the input shaft 13. The forward clutch 14 connects or disconnects the power transmission from the input shaft 13 to the forward output shaft 52, and the reverse clutch 15 connects or disconnects the power transmission from the input shaft 13 to the propeller shaft 6. The hydraulic pump 19 (refer to FIG. 25), which supplies hydraulic oil to the forward clutch 14 and the reverse clutch 15, is coupled to the front end section of the reverse output shaft 51. A forward reduction drive gear 54 is fixed to the front end section of the forward output shaft 52.

The reverse reduction gear 45, which is loosely fitted to the reverse output shaft 51, and the forward reduction drive gear 54, which is fixed to the forward output shaft 52, are constantly engaged with the reduction output gear 35 of the propeller shaft 6. In this reference example, the input gear 13 a, the input relay gear 14 g, the forward reduction gear 43, the reverse reduction gear 45, and the forward relay gear 53 are helical gears, and the reduction output gear 35 and the forward reduction drive gear 54 are conical gears. The gears 13 a, 14 g, 43, and 53 may be other gears such as spur gears.

In the reverse gear 50, the forward/reverse switching mechanism 20 includes the input gear 13 a, the input relay gear 14 g, the forward clutch 14, the reverse clutch 15, the reverse output shaft 51, the forward output shaft 52, the forward reduction gear 43, and the forward relay gear 53. The reduction mechanism 17 includes the reduction output gear 35, the reverse reduction gear 45, and the forward reduction drive gear 54. The reverse reduction gear 45 and the forward reduction drive gear 54 each configure a drive gear of the reduction output gear 35.

When the forward/reverse lever in the cockpit 3 is manipulated to the forward, reverse, or neutral position, the supply destination of the hydraulic oil is shifted to the forward clutch 14, the reverse clutch 15, or neutral. When the forward/reverse lever is manipulated to the forward position, the forward clutch 14 is brought into the power connected state, and the reverse clutch 15 is in the power disconnected state. Thus, the forward clutch 14 causes the forward reduction gear 43 to rotate integrally with the reverse output shaft 51. In this state, the rotational power of the engine 10 is transmitted from the input shaft 13 to the forward output shaft 52 via the reverse output shaft 51 and the forward clutch 14, and the forward output shaft 52 is rotated in the same direction as the input shaft 13. The rotational force is transmitted from the forward output shaft 52 to the propeller shaft 6 via the reduction mechanism 17. As a result, the watercraft 1 is brought into the forward state in which the rotational power of the engine 10 is transmitted to the propeller shaft 6 as the output in the forward direction. In the forward state, the rotational power of the input shaft 13 is reduced in accordance with the reduction ratio of the input gear 13 a and the input relay gear 14 g, the reduction ratio of the forward reduction gear 43 and the forward relay gear 53, and the reduction ratio of the forward reduction drive gear 54 and the reduction output gear 35. The rotational power that has been reduced is transmitted to the propeller shaft 6.

When the forward/reverse lever is manipulated to the reverse position, the reverse clutch 15 is brought into the power connected state, and the forward clutch 14 is in the power disconnected state. Thus, the reverse clutch 15 causes the reverse reduction gear 45 to rotate integrally with the reverse output shaft 51, which is rotated in reverse to the input shaft 13. Thus, the rotational power of the engine 10 is transmitted from the input shaft 13 to the propeller shaft 6 via the reverse output shaft 51 and the reverse clutch 15. As a result, the watercraft 1 is brought into the reverse state in which the rotational power of the engine 10 is transmitted to the propeller shaft 6 as the output in the reverse direction. In the reverse state, the rotational power of the input shaft 13 is reduced in accordance with the reduction ratio of the input gear 13 a and the input relay gear 14 g and the reduction ratio of the reverse reduction gear 45 and the reduction output gear 35 and is transmitted to the propeller shaft 6.

When the forward/reverse lever is manipulated to the neutral position to bring both the forward clutch 14 and the reverse clutch 15 into the power disconnected state, the watercraft 1 is brought into the neutral state in which the rotational power is not transmitted to the propeller shaft 6. Although both the clutches 14 and 15 are in the power disconnected state, the rotational power of the input shaft 13 is transmitted to the reverse output shaft 51 via the input gear 13 a and the input relay gear 14 g. Thus, the hydraulic pump 19, which is coupled to the front end section of the reverse output shaft 51, is operated.

Compared with the reverse gear 11 of the above-described first to sixth embodiments (seven helical gears and two conical gears), the reverse gear 50 (five helical gears and two conical gears) uses a reduced number of gears. This simplifies the configuration of the reverse gear 50 and reduces the manufacturing costs.

Since both the forward clutch 14 and the reverse clutch 15 are provided on the reverse output shaft 51, the reverse gear 50 is capable of supplying oil to the clutches 14 and 15 through an oil passage in the reverse output shaft 51. In contrast, in the reverse gear 11 of the above-described first or second embodiment, the forward clutch 14 and the reverse clutch 15 are provided separately on the forward clutch shaft 14 f and the reverse clutch shaft 15 f. The oil is supplied to the clutches 14 and 15 through oil passages in the clutch shafts 14 f and 15 f. Such an internal oil passage is formed by gun drilling. Thus, compared with the reverse gear 11 of the above-described first or second embodiment (in which the clutch shafts 14 f and 15 f each include the internal oil passage), the reverse gear 50 (in which the reverse output shaft 51 includes the internal oil passage) has a reduced number of shafts that include the internal oil passage. That is, the number of shafts that use the gun drill is reduced. This simplifies the configuration of the reverse gear 50 and reduces the manufacturing costs.

Both the forward clutch 14 and the reverse clutch 15 of the reverse gear 50 are provided on the reverse output shaft 51. The clutch cases of the clutches 14 and 15 are shrink-fitted to the reverse output shaft 51. In contrast, in the reverse gear 11 of the above-described first or second embodiment, the forward case 14 a of the forward clutch 14 is shrink-fitted to the forward clutch shaft 14 f, and the reverse case 15 a of the reverse clutch 15 is shrink-fitted to the reverse clutch shaft 15 f. Thus, the reverse gear 50 (in which the number of the shrink-fitted shaft is one) has a reduced number of the shrink-fitted shaft compared with the reverse gear 11 (the number of the shrink-fitted shaft is two) of the above-mentioned embodiments. This configuration reduces the number of processes for assembling the reverse gear 50 and reduces the manufacturing costs.

As clearly shown in the above description and FIGS. 22 to 25, the reverse gear 50 includes the input shaft 13, the forward/reverse switching mechanism 20, the reverse output shaft 51, the forward output shaft 52, and the reduction mechanism 17. The input shaft 13 receives rotational power of the engine 10, which is the main engine. The forward/reverse switching mechanism 20 switches the rotational power of the input shaft 13 among the forward, neutral, and reverse states. The reverse output shaft 51 and the forward output shaft 52 output the rotational power of the forward/reverse switching mechanism 20. The reduction mechanism 17 reduces the rotational power of the output shafts 51 and 52 and transmits the reduced rotational power to the propeller shaft 6. Since the forward/reverse switching mechanism 20 has the reduction function, the rotational speed of the input shaft 13 differs from the rotational speed of the reverse output shaft 51, and the rotational speed of the input shaft 13 differs from the rotational speed of the forward output shaft 52. The reduction mechanism 17 transmits the rotational power of the output shafts 51 and 52 to the propeller shaft 6 by the engagement of the reverse reduction gear 45 and the forward reduction drive gear 54, which are provided on the output shafts 51 and 52, with the reduction output gear 35, which is provided on the propeller shaft 6. Thus, while the reverse gear 50 obtains a desired reduction ratio by the combination of the forward/reverse switching mechanism 20 and the reduction mechanism 17, the number of the gears constituting the reduction mechanism 17 is reduced. This reduces the size of the reduction mechanism 17 and the space occupied by the reduction mechanism 17 and consequently reduces the size of the entire reverse gear 50 and the space occupied by the entire reverse gear 50. This configuration improves the versatility of the reverse gear 50 and enables the reverse gear 50 to be mounted on the watercraft 1 that has a limited height.

In the reverse gear 50, the height of the housing of the reduction mechanism 17 is reduced, and the length of the housing of the reduction mechanism 17 in the axial direction is reduced by reducing the number of the gears constituting the reduction mechanism 17. Thus, the space in the watercraft such as the occupant's space S (refer to FIG. 1) is increased. This configuration provides a space for mounting the seat 7 above the reduction mechanism 17 and enables the reverse gear 50 to be mounted on the watercraft 1 that has a limited height.

In the reverse gear 50, the forward/reverse switching mechanism 20 includes the input gear group (the input gear 13 a and the input relay gear 14 g), which includes a plurality of gears engaged with each other. The reduction ratio of the forward/reverse switching mechanism 20 is changed by replacing the input gear group. Thus, a plurality of reduction ratios can be selected by the combination of the forward/reverse switching mechanism 20 and the reduction mechanism 17 without changing the reduction ratio of the reduction mechanism 17. This configuration improves the ease in variation development of the reverse gear 50 while achieving the commonality of the reduction mechanism 17 among models and specifications and contributes to improving the versatility and increasing the range of application of the reverse gear 50.

In the reverse gear 50, the forward/reverse switching mechanism 20 may include the forward clutch 14 and the reverse clutch 15 that have different clutch sizes from each other. For example, the clutch size of the reverse clutch 15 may be smaller than the clutch size of the forward clutch 14. Thus, the size of the forward/reverse switching mechanism 20 and the space occupied by the forward/reverse switching mechanism 20 are reduced. This consequently reduces the size of the reverse gear 50 and the space occupied by the reverse gear 50.

In the reverse gear 50, the forward clutch 14 and the reverse clutch 15 may be swapped so that the rotational power of the input shaft 13 is transmitted to the propeller shaft 6 via the output shaft 51 as the forward output, and the rotational power of the input shaft 13 is transmitted to the propeller shaft 6 via the output shafts 51 and 52 as the reverse output.

The configuration of each part of the embodiments of the present invention is not limited to the illustrated embodiments, but may be modified in various forms without departing from the scope of the invention.

For example, the reduction mechanism 17 is not limited to a V-drive system, but may be an angle drive system or a parallel shaft system. 

What is claimed is:
 1. A reverse gear for watercrafts comprising: an input shaft configured to receive rotational power of a main engine; a forward/reverse switching mechanism comprising a reduction function and configured to switch the rotational power of the input shaft among forward, neutral, and reverse states; an output shaft configured to output the rotational power of the forward/reverse switching mechanism and to rotate at a rotational speed that differs from a rotational speed of the input shaft due to the reduction function of the forward/reverse switching mechanism; a reduction mechanism comprising a fixed reduction ratio and configured to reduce the rotational power of the output shaft and to transmit the reduced rotational power to a propeller shaft; a forward/reverse housing accommodating the forward/reverse switching mechanism; and a reduction housing accommodating the reduction mechanism, the forward/reverse housing and the reduction housing are detachably coupled one behind the other in an axial direction of the output shaft.
 2. The reverse gear for watercrafts according to claim 1, wherein the forward/reverse switching mechanism comprises at least one of an input gear group and an output gear group, the input gear group and the output gear group each comprises a plurality of gears engaged with one another, and the forward/reverse switching mechanism comprises a reduction ratio that is changed by replacing at least one of the input gear group and the output gear group.
 3. The reverse gear for watercrafts according to claim 1, wherein the forward/reverse switching mechanism comprises a forward clutch and a reverse clutch that differ in a clutch size from each other. 